50.5 Calcium And Regulatory Proteins

Question 1

what role does Ca2+ play?

Answer 1

–at low Ca2+ concentrations, tropomyosin and troponin complex cover the binding sites on the actin (thin filaments)

–when Ca2+ accumulates in the cytosol, it binds to the troponin complex causing proteins to shift position and expose the actin binding sites.

Question 2

how dod motor neurons cause contractions?

Answer 2

they trigger release of Ca2+ into the cytosol of muscle cells -

Question 3

skeletal muscle contraction diagram

Answer 3

Transverse Tubules (T tubule)

-Sarcoplasmic reticulum (SR)

Question 4

skeletal muscle contraction

Answer 4

1) acetylcholine release and bind to receptor proteins (channels open) that make an action potential (depolarization)
2) the action potential travels down T tubules triggering release of Ca2+ from the SR
3) Ca2+ binds to troponin
4) myosin cross bridges attach to actin and pull it towards the center
5) active transport of Ca2+ out into SR to prepare for next contractions